When designing capacitive MEMS devices, e.g. sound transducers, pressure sensors, acceleration sensors, microphones or loudspeakers, it may be typically desirable to achieve a high signal-to-noise ratio (SNR) of the transducer output signal. The continuous miniaturization of transducers may pose new challenges with respect to the desired high signal-to-noise ratio. MEMS microphones and to the same extent also MEMS loudspeakers which may be used in, for example, mobile phones, laptops, and similar (mobile or stationary) devices, may nowadays be implemented as semiconductor (silicon) micro-phones or microelectromechanical systems (MEMS). In order to be competitive and to provide the expected performance, silicon microphones may need a high SNR of the microphone output signal. However, taking the capacitor microphone as an example, the SNR may be typically limited by the capacitor microphone construction and by the resulting parasitic capacitances.
Parasitic capacitances are usually unwanted capacitances interfering with capacitances between the membrane and the counter electrode. Hence, capacitance values, which are intended to be transferred into electrical signals in response to the movement of the membrane relative to the counter-electrode, are interfered. In case the MEMS device is embodied as a MEMS microphone, for example, parasitic capacitances may influence the MEMS microphone such that the electrical output signal does not provide a sufficiently correct reproduction of the audible sound input signal, i.e. the arriving soundwaves or sound pressure changes.